The invention relates to a robot for vacuum cleaning surfaces, which robot is provided with a housing, a suction unit accommodated in said housing, a suction nozzle mounted to the housing, which suction nozzle is situated, during operation, close to a surface to be vacuum cleaned, a motor-drivable wheel system by means of which the housing can be displaced over the surface to be cleaned, and an electrical control member for controlling a displacement of the housing to be generated by means of the wheel system.
Robots of the type mentioned in the opening paragraph are generally known. The control member of such robots controls the wheel system in such a manner that the robot automatically carries out predetermined displacements, or random displacements, over the surface to be cleaned, so that after some time the robot has reached and treated all parts of the surface. Such robots are generally provided with sensors that co-operate with the control member, so that obstacles are avoided as much as possible during displacements of the robot over the surface. Such robots are preferably provided with a battery or accumulator to feed the suction unit, the control member and the drive unit for the wheel system, so that an electrical cord connection is not necessary for this robot. Such a cord connection could hamper or limit the freedom of displacement of the robot.
Batteries and accumulators which can suitably be used in such robots generally have a sufficiently large energy capacity but only a limited power. As a result, the suction unit of such robots has only a limited suction power. In order to make sure that, in spite of the limited suction power, a sufficiently large suction force of the suction nozzle is obtained, i.e. a sufficient underpressure in the suction nozzle, the suction nozzle of such robots generally has limited dimensions. Consequently, a drawback of such robots is that the suction range, i.e. the width of a path treated by the robot during a displacement of the robot along a line of displacement, is limited so that the robot must carry out a comparatively large number of displacements to treat the whole surface to be cleaned. As a result, such robots need a comparatively large amount of time to treat the entire surface area. This drawback is even more manifest in robots of the type mentioned in the opening paragraph which carry out random displacements over the surface, for which the number of necessary displacements will generally substantially exceed the number of necessary displacements of robots carrying out predetermined displacements.
It is an object of the invention to provide a robot of the type mentioned in the opening paragraph, which robot also has a suction nozzle of limited dimensions, but the suction range of which, as defined hereinabove, is increased substantially.
To achieve this object, a robot in accordance with the invention is characterized in that the displacement controlled by the control member comprises a substantially cycloid movement that is brought about by a rolling motion of an imaginary rolling circle along an imaginary line of displacement of the housing over the surface to be cleaned, the suction nozzle being eccentrically arranged with respect to the rolling circle, which rolling circle extends parallel to the surface to be cleaned and is fixed with respect to the housing. Said cycloid movement not only causes the housing to be moved over the surface in accordance with said line of displacement, but also to be simultaneously rotated about an axis of rotation extending perpendicularly to the surface and through the center of the rolling circle. As the suction nozzle is eccentrically arranged with respect to the rolling circle, the suction nozzle does not move rectilinearly in accordance with the line of displacement, but follows a cycloid that is situated on either side of the line of displacement. By virtue thereof, viewed perpendicularly to the line of displacement, the suction nozzle covers a comparatively wide path of the surface to be cleaned during the displacement of the housing along the line of displacement, so that the suction range, i.e. the width of the path treated by the robot during the displacement of the robot along the line of displacement, is comparatively large.
A particular embodiment of a robot in accordance with the invention is characterized in that the wheel system comprises at least three wheels arranged at regular intervals in accordance with an imaginary base circle, each wheel having a wheel axle extending in accordance with a radial of the base circle and being drivable by means of a separate motor, and each wheel being provided, along its circumference, with a number of rolls each having a roll axle extending in a tangential direction with respect to the wheel axle of the relevant wheel. By means of a suitable, comparatively simple control of the individual motors of the wheels of said wheel system, the housing is displaceable over the surface to be cleaned, in this particular embodiment, in any direction in accordance with a straight or curved line of displacement, rotatable about an axis of rotation extending perpendicularly to the surface, or simultaneously displaceable in accordance with such a line of displacement and rotatable about such an axis of rotation. In this manner, the robot has substantial freedom of movement, and the wheel system can particularly suitably be used to generate the desired cycloid movement of the housing. As each wheel is provided, along its circumference, with said rolls, the individual wheels cannot only be displaced in a customary direction perpendicular to the wheel axles, but also in a direction parallel to the wheel axles. By virtue thereof, a desired displacement of the housing, which can be generated by a suitable rotation of one or more of the wheels about their wheel axles, is not hampered or prevented by insufficient freedom of movement of the other wheels.
A further embodiment of a robot in accordance with the invention is characterized in that the rolling circle is concentric with the base circle, while the radius of the rolling circle is at the most equal to approximately WS/2xcfx80, where WS is a main dimension of the suction nozzle, measured along a radial of the base circle. As the radius of the rolling circle is at most equal to approximately WS/2xcfx80, during one complete revolution of the housing about the axis of rotation, the housing is displaced along the line of displacement over a distance which is at most equal to WS. As the suction nozzle thus is displaced, during one complete revolution of the housing, along the line of displacement over a distance that is at most equal to the main dimension of the suction nozzle, measured along the radial of the base circle, the parts of the path, that is treated by the suction nozzle during a number of successive revolutions of the housing, blend substantially without interspace, viewed in the direction of the line of displacement, so that the robot does not leave parts of the path untreated as a result of the rotating movement.
Yet another embodiment of a robot in accordance with the invention is characterized in that the suction nozzle extends, viewed along said radial of the base circle, substantially up to said base circle. In this further embodiment, the path treated by the suction nozzle during the displacement of the housing in accordance with the line of displacement, has a width that substantially corresponds to the diameter of the base circle. If the wheels are arranged near the circumference of the housing, the width of the path thus corresponds substantially with a principal dimension of the housing, so that the width of the path treated by said robot is clearly visualized to the user of the robot.
A particular embodiment of a robot in accordance with the invention is characterized in that the radius of the rolling circle is smaller than approximately 0.16. RB, where RB is the radius of the base circle. In this particular embodiment, the principal dimension of the suction nozzle, measured along the radial of the base circle, is at most equal to the radius of the base circle. It has been found that such a principal dimension of the suction nozzle in combination with customary batteries or accumulators results in a sufficient suction force of the suction nozzle, i.e. a sufficient underpressure in the suction nozzle is obtained.